Quake

The Quake Soundtrack was wholly created by Trent Reznor and NIN for use as background and incidental music during gameplay. The 10 tracks created for this release have never been released elsewhere, and therefore an original copy of the soundtrack (which appears on the same disc as the game) is prized by many.

Doom 3

Reznor was originally approached to create sound effects and music for Doom 3, and his pieces were used in the original alpha release. However, the final game didn't contain any music or sounds by Reznor. Chris Vrenna did the job instead.

NIN logo is present as easter egg in The Ultimate DOOM level "E4M1: Hell Beneath" designed by American McGee [1].

Tony Hawk's Project 8

Tap Tap Revenge

The iPhone exclusive game Tap Tap Revenge premiered its first ever special edition version of the game with Tap Tap Revenge: Nine Inch Nails, featuring 13 tracks from Ghosts I-IV and The Slip, hand-picked by Reznor. This is also the first game that was co-designed by Reznor, along with long-time art director Rob Sheridan, highlighting a desire that both have pledged for making a full-blown video game.
The tracks used are: